feat: add cache tokens to Models and Providers panels, unify column layout

[white-hat]

I wanted to check how caching differs from model to model and realized that your app lacks exactly that info. So I added it, and while at it — made the layout consistent across panels so you don't have to re-scan when switching pages.

Summary

• Add cache_tokens field to ModelUsageRow and ProviderUsageRow
• Aggregate cache_tokens from cache_read + cache_write in both model and provider chart builders
• Switch Models and Providers detail panels from 3-column to 2-column layout (5 rows)
• Unify field ordering across Models, Providers, and Overview panels so users don't have to re-scan when switching pages

Layout

Before (3 columns × 3 rows, no Cache row):

Tokens   Cost     Sessions
Input    Output   Messages
Prompts  Days     Rate

After (2 columns × 5 rows, with Cache):

Tokens   Cost
Input    Sessions
Output   Messages
Cache    Prompts
Rate     Days

This matches the Overview panel's 2-column layout and makes navigation between panels more consistent.

[Cateds]

If the compressed line chart remains reasonably readable ...
I previously compressed the description to fit the data into 3 rows (as "Total cost: " -> "Cost "), let me convert it back if 2 rows is back.

[Cateds]

Oh, and thanks for your contribution!